Subversion Repositories simple_fm_receiver

-- $Id: fm.vhdl,v 1.1.1.1 2005-01-04 02:05:58 arif_endro Exp $

-------------------------------------------------------------------------------

-- Title       : FM core component

-- Project     : FM Receiver 

-------------------------------------------------------------------------------

-- File        : fm.vhdl

-- Author      : "Arif E. Nugroho" <arif_endro@yahoo.com>

-- Created     : 2004/12/06

-- Last update : 2005/01/03 

-- Simulators  : Modelsim 6.0

-- Synthesizers: 

-- Target      : 

-------------------------------------------------------------------------------

-- Description : FM core component to connect all other component

-------------------------------------------------------------------------------

-- Copyright (c) 2004 Arif E. Nugroho

-- This VHDL design file is an open design; you can redistribute it and/or

-- modify it and/or implement it after contacting the author

-------------------------------------------------------------------------------

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_arith.ALL;

entity fm is

 port (

  CLK                     : in  bit;

  RESET                   : in  bit;

  FMIN                    : in  bit_vector (07 downto 0);

  DMOUT                   : out bit_vector (11 downto 0)

  );

end fm;

architecture structural of fm is

 component nco

  port (

       clock              : in  bit;

       clear              : in  bit;

       input_nco          : in  bit_vector (17 downto 0);

       offset             : in  bit_vector (17 downto 0);

       output_nco         : out bit_vector (07 downto 0)

       );

 end component;

 component loop_filter

  port (

       input_loop         : in  bit_vector (07 downto 0);

       clock              : in  bit;

       output_loop        : out bit_vector (11 downto 0);

       clear              : in  bit

       );

 end component;

 component phase_detector

  port (

       clock              : in  bit;

       signal_input       : in  bit_vector (07 downto 0);

       signal_nco         : in  bit_vector (07 downto 0);

       phase_output       : out bit_vector (07 downto 0)

       );

 end component;

 component fir

  port (

       clock              : in  bit;

       clear              : in  bit;

       fir_in             : in  bit_vector (11 downto 0);

       dmout              : out bit_vector (11 downto 0)

       );

 end component;

-- internal signal

signal loop_out           : bit_vector (11 downto 0);

signal input_nco          : bit_vector (17 downto 0);

signal offset             : bit_vector (17 downto 0);

signal output_nco         : bit_vector (07 downto 0);

signal phase_output       : bit_vector (07 downto 0);

begin

-- offset values 1/16 equ B"000100000000000000" <18,0,u>

offset (17) <= '0' ;

offset (16) <= '0' ;

offset (15) <= '0' ;

offset (14) <= '1' ;

offset (13) <= '0' ;

offset (12) <= '0' ;

offset (11) <= '0' ;

offset (10) <= '0' ;

offset (9)  <= '0' ;

offset (8)  <= '0' ;

offset (7)  <= '0' ;

offset (6)  <= '0' ;

offset (5)  <= '0' ;

offset (4)  <= '0' ;

offset (3)  <= '0' ;

offset (2)  <= '0' ;

offset (1)  <= '0' ;

offset (0)  <= '0' ;

-- The constant that have great effect on the loop

-- it's a 1/16 divider it's has 5 step to change the output state with little

-- oscillation. it's can be make good shape by reducing the constant e.g 1/32

-- but it's has slower response time than 1/16 about 2 times e.g approx 10 step

-- to change the output state. if it's too big e.g (1) then there is no output

-- only oscilation if it's is to small e.g (1/1024) then output never return to

-- zero, so it's didn't change the output state.

input_nco (17) <= loop_out(11); -- 1

input_nco (16) <= loop_out(11); -- 1/2

input_nco (15) <= loop_out(11); -- 1/4

input_nco (14) <= loop_out(11); -- 1/8

input_nco (13) <= loop_out(11); -- 1/16

input_nco (12) <= loop_out(10); -- 1/32

input_nco (11) <= loop_out(09); -- 1/64

input_nco (10) <= loop_out(08); -- 1/128

input_nco (09) <= loop_out(07); -- 1/256

input_nco (08) <= loop_out(06); -- 1/512

input_nco (07) <= loop_out(05); -- 1/1024

input_nco (06) <= loop_out(04);

input_nco (05) <= loop_out(03);

input_nco (04) <= loop_out(02);

input_nco (03) <= loop_out(01);

input_nco (02) <= loop_out(00);

input_nco (01) <= loop_out(11);

input_nco (00) <= loop_out(11);

-- end divider 

mynco : nco

    port map (

    clock                      => CLK,

    clear                      => RESET,

    input_nco                  => input_nco,

    offset                     => offset,

    output_nco ( 7 downto 0)   => output_nco

    );

myfir : fir

    port map (

    clock                      => CLK,

    clear                      => RESET,

    fir_in                     => loop_out,

    dmout (11 downto 0)        => DMOUT

    );

myphase : phase_detector

    port map (

    clock                      => CLK,

    signal_input               => FMIN,

    signal_nco                 => output_nco,

    phase_output ( 7 downto 0) => phase_output

    );

myloop : loop_filter

    port map (

    input_loop                 => phase_output,

    clock                      => CLK,

    output_loop (11 downto 0)  => loop_out,

    clear                      => RESET

    );

end structural;